The present invention relates to improving the lamp lumen depreciation performance of metal halide HID lamps. More particularly, the invention relates to much improved lamp lumen depreciation performance of Pulse Arc Metal Halide lamps when used with an electronic ballast.
There has been an industry wide problem in meeting lamp lumen depreciation (LLD) specifications for metal halide (MH) lamps for some time now. In general, the LLD performance has been lower than rated or desirable, and considerable effort over the last 30 years has been spent on trying to solve this problem. Two independent efforts to solve this problem have involved a new lamp/ballast system called Pulse Arc or Pulse Start and separate work on electronic ballasts to improve the performance of standard MH lamps.
The first effort involves increasing the fill pressure in the arc tube of a MH lamp, using a shaped arc tube and eliminating the starter electrode and associated components (bi-metal switch and resistor). An igniter pulse-forming network is then required to start this new lamp. The system is generally referred to as Pulse Arc or Pulse Start.
The second effort involves the use of a high frequency electronic ballast where the 60 Hz output frequency is replaced with a 90 kHz output frequency with a sine wave of voltage and current. One example of a ballast designed to operate lamps at 90 kHz is a Delta Power ballast (Delta Power Supply, Inc.). We have found through testing that this ballast will generally improve the LLD of standard MH lamps.
It would be desirable to combine the two aforementioned efforts to compound the benefits of both efforts for greater improvements than either effort by itself can provide, however, an impediment to combining the efforts has been that the available high frequency ballasts were not designed to operate Pulse Arc lamps and would not start them.
A desirable aspect of the present invention is that it provides the advantages and compounded benefits of both heretofore uncombined efforts to improve LLD performance of MH lamps. Still a further desirable aspect of the present invention is that it provides the compounded benefits to as wide a range of lamp wattages as possible, thereby simplifying the design of lamp/ballast lighting systems in general.
In an embodiment of the present invention,. a high frequency 90 kHz electronic ballast is used to provide starting pulses capable of starting Pulse Arc MH and Pulse Start MH lamps. The ballast is further designed to operate the aforementioned lamps at wattages at least as high as 400 watts. The combination of Pulse Arc and Pulse Start MH lamps with a modified 90 Khz electronic ballast provides LLD performance for MH lamps previously unmatched in the industry.